Have you tried all the solvents on the Galactic Swirl?
I start with water and then move on to solvents.
Solvents are in 2 groups, petroleum and alcohol, if I remember correctly.
I start with the alcohol family and then the petroleums.
I have not experimented with citrus, and these can be very strong. After
hearing about lens coating damage from citrus I stopped buying any soaps or
cleaners with citrus but it may be worth a try if the lens is uncoated.